Double parton distributions in the nucleon from lattice QCD

Abstract

We evaluate nucleon four-point functions in the framework of lattice QCD in order to extract the first Mellin moment of double parton distributions (DPDs) in the unpolarized proton. In this first study, we employ an nf = 2+1 ensemble with pseudoscalar masses of mπ = 355 MeV and mK = 441 MeV. The results are converted to the scale μ = 2 GeV. Our calculation includes all Wick contractions, and for almost all of them a good statistical signal is obtained. We analyze the dependence of the DPD Mellin moments on the quark flavor and the quark polarization. Furthermore, the validity of frequently used factorization assumptions is investigated.

Evolution and interpolation of double parton distributions using Chebyshev grids

“…They quantify a variety of correlations between two partons in the proton [19,20,27] and thus reveal aspects of hadron structure that are not accessible in ordinary parton distributions (PDFs). Our knowledge of DPDs is still quite limited, although there is considerable activity in devising theory guided ansätze [28][29][30][31] and in computing DPDs using lattice QCD [32] or quark models [33][34][35][36][37][38][39][40].…”